Lighting devices such as lamps or bulbs are designed to produce light from electricity. With rapid development of industrial techniques, these lighting devices become essential components in our daily lives because they can improve the living quality. In the early stage, lighting devices are used for simply providing a bright place. With diversified living attitudes, in addition to the illuminating purpose, proper lighting devices can enhance task performance or aesthetics. For complying with various demands, the lighting devices should be designed to have desired sizes or produce light with desired irradiation position, orientation, inclination or intensity.
For example, especially for the large-scale stage designs or small-scale cabin illumination systems, it is very important to adjust the orientation and inclination of incident light. Conventionally, there are two types of mechanisms for adjusting the orientation and inclination of incident light. These three mechanisms are designed according to the configurations, light sources or light path switching structures.
FIG. 1 is a schematic diagram illustrating a first type lighting device for adjusting the orientation and inclination of incident light. Such a lighting device is disclosed in for example U.S. Pat. No. 5,690,417, and the contents of which are hereby incorporated by reference. As shown in FIG. 1, the lighting device 10 principally comprises a light source group 11. The light source group 11 comprises a plurality of lamps. These lamps can be inclined at different angles so as to adjust the orientation and inclination of incident light. As a consequence, the light beams emitted by the lamps can be selectively directed to a workpiece 13 on a work table 12. This lighting device, however, still has some drawbacks. For example, a great amount of light sources are required in this lighting device 10. In addition, the control system for this lighting device 10 is very complicated. In a case that the lamps are selectively turned on and turned off while changing orientation and inclination of incident light, discontinuous illumination will possibly occur.
FIG. 2 is a schematic diagram illustrating a second type lighting device for adjusting the orientation and inclination of incident light. Such a lighting device is disclosed in for example U.S. Pat. Nos. 3,912,918, 5,070,434 and 6,461,024, and the contents of which are hereby incorporated by reference. For reducing the overall volume and saving the fabricating cost, the orientation and inclination of incident light for the lighting device 30 are manually controlled. A light source is mounted inside a casing 31 and a cone member 32. The casing 31 may be fixed or supported by a specified apparatus. A shaft 34 is secured to a ball assembly 33. By rotating the ball assembly 33, the cone member 32 is adjusted to a desired position as shown in dotted line such that orientation and inclination of incident light are adjustable. This lighting device 30 is applicable to cabin illumination systems or other small-scale illumination systems. The manual operation of such a lighting device is not convenient. In addition, it is labor-intensive to rotate the cone member and the ball assembly.
Therefore, there is a need of providing an improved lighting device and a method of operating such a lighting device to obviate the drawbacks encountered from the prior art.